The present invention relates to unbaked, porcelain teeth and methods of making the same. More specifically, the present invention relates to water-resistant, unbaked, porcelain teeth and methods of making the same.
In the art of manufacturing prosthetic dental appliances, there are several procedures for manufacturing porcelain teeth therefor. However, certain basic steps are followed in all such procedures. These include forming a porcelain paste of porcelain and an agglutinant or binder, molding to the approximate shape of the desired tooth, drying to remove moisture and harden the agglutinant or binder, heating to an elevated temperature to vitrify the porcelain, soaking at this temperature to glaze the outside surfaces and shaping and fitting the tooth to the patient's exact needs and fitting it to the appliance by grinding or adding porcelain as needed, usually in a dental laboratory under the direction and instruction of the dentist.
In accordance with one standard procedure, fully vitrified porcelain teeth are sold in the completely finished state. A tooth is then selected that approximately meets the requirements in a particular case and is then fitted exactly to the patient's requirements and to the appliance by grinding and/or adding porcelain of a lower fusion point than that of the porcelain utilized in the manufacture of the tooth. The modified tooth is then fired to make it a somewhat integral structure with the added porcelain. However, in working with such completely vitrified porcelain teeth, numerous difficulties are encountered. First, such completely vitrified teeth are hard and brittle and are, therefore, difficult to grind. In addition, such grinding violates the integrity of the surface of the tooth. Finally, only porcelain of a lower fusion point than that of the tooth proper can be added to build-up the tooth where necessary. Since the fully vitrified tooth is hard and nonporous, the added porcelain cannot diffuse into the tooth proper, thus resulting in a final structure which cannot be considered a monolithic or homogeneous structure, and has a poor bond or juncture between the tooth proper and the added porcelain, even after firing to full vitrification. It is also obvious that the added porcelain will have a somewhat lower structural strength than the tooth proper.
In order to overcome the disadvantages of shaping and fitting the hard, brittle, fully vitrified tooth and make possible the addition of porcelain of the same fusion point, it is also common practice to make porcelain teeth in the unbaked or "green" state, and, thereafter, fire the tooth to the fusion or vitrification point. More specifically, a porcelain paste is formed of porcelain and an agglutinant or binder, the paste is shaped or molded to the desired shape and contour and the shaped tooth is then dried at a low temperature, about 600.degree. F., to remove moisture and harden the agglutinant or binder. In this state, the tooth is oversized (about twice the size of the finished tooth), is easily damaged and is difficult to handle and shape and fit. These drawbacks are attributable to the nature of the agglutinants presently utilized in the formation of the green tooth. All presently used agglutinants, such as starch, lose their adhesive properties when exposed to water either due to the fact that they are water-soluble or are destroyed during the drying step. As a result, the green tooth tends to disintegrate when moistened. This makes it impossible to adapt the tooth, since moist porcelain must usually be added. It has also been found that the green tooth is generally held together by an adhesive film on the surface and the interior is powdery and incohesive. Thus, upon grinding, the powdery or unconsolidated interior is exposed. This characteristic structure is believed to be caused by the fact that many presently used agglutinants are expelled from the porcelain during the process of drying the shaped structure. Finally, agglutinants presently used are usually of vegetable origin (generally a starch) and such agglutinants burn when the tooth is fired to the fusion or vitrification temperature. As a result, a small amount of residue or ash is produced which causes some discoloration of the finished, vitrified tooth.
Yet another commercial technique is set forth in Applicant's U.S. Pat. Nos. 3,621,576 and 3,766,650, the teachings of which are incorporated herein by reference. In accordance with this technique, teeth are supplied to the customer in a semi-baked state and the customer is instructed to adapt the tooth and thereafter fire the same to the vitrification temperature. This technique overcomes the disadvantages of working with hard, brittle fully-vitrified teeth and permits the addition of porcelain having the same fusion point as the tooth proper during adaptation. In summary, a tooth is prepared, in accordance with the above-mentioned patents, by making a green tooth or biscuit in the usual manner and then baking the biscuit at a temperature which converts it to a hard, concretious or consolidated state (above about 1200.degree. F.) but below the vitrification or fusion point of the porcelain utilized (usually about 50.degree. F. below the fusion point). In this state, the tooth is water-insoluble, is essentially resistant to damage, during handling and adapting, has a rough, porous surface, which accepts porcelain of the same fusion point as the tooth proper, after firing to vitrification, forms a monolithic or homogeneous structure of the tooth proper and the added porcelain and is substantially the same size as the fully vitrified or finished tooth. The customer then adapts the tooth, as indicated above, and fires it to the vitrification point of about 1600.degree. F. or 2300.degree. F. or higher, depending upon whether the porcelain utilized has a low or high temperature fusion point. While this technique overcomes numerous of the disadvantages of working with green, unbaked teeth, at the customer level, particularly the problem of water-solubility, certain problems are still associated with the handling of and working with the biscuit during the manufacture of such semi-baked teeth. For example, the green tooth must be adapted to some degree, by trimming and sometimes adding porcelain prior to the semi-baking step, and the handling and working of the tooth at this stage is facilitated by practicing the present invention in the preparation of the green tooth prior to the semi-baking step.
It is, therefore, an object of the present invention to provide an improved porcelain tooth and a method of manufacture which overcomes the previously-mentioned disadvantages of the prior art.
Another object of the present invention is to provide an improved green, porcelain tooth and method of manufacture.
Yet another object of the present invention is to provide an improved semi-baked porcelain tooth and method of manufacture.
A further object of the present invention is to provide a water-resistant, green, porcelain tooth and method of manufacture.
Another and further object of the present invention is to provide an improved green, porcelain tooth, and method of manufacture, which can be molded in any molding apparatus, such as a solid plaster or metal mold, a semi-solid wax or plastic mold, an elastic or rubber mold, etc.
A still further object of the present invention is to provide an improved green, porcelain tooth, and method of manufacture, which is rugged and easy to handle.
Another object of the present invention is to provide an improved green, porcelain tooth, and method of manufacture, which can be cut, shaped, handled and adapted without affecting its structure, as its basic form, color, strength, etc.
A further object of the present invention is to provide an improved green, porcelain tooth, and method of manufacture, which can be adapted, as by trimming, grinding, adding porcelain, etc. witout affecting its structure.
Yet another object of the present invention is to provide an improved green, porcelain tooth, and method of manufacture, which can be converted to an improved finished or completely vitrified tooth, as a finished tooth of reduced, desired size and shape, etc.
Another object of the present invention is to provide an improved green porcelain tooth and method of manufacture, which is of uniform or homogeneous structure throughout, as consistency and cohesiveness, as opposed to a non-homogeneous or non-uniform structure, as a powdery interior, a non-uniform and/or different structure between the tooth proper and porcelain added during adaptation, a weak or improper bond between the tooth proper and porcelain added during adaptation, etc.
A further object of the present invention is to provide an improved green, porcelain tooth and method of manufacture which results in reduced waste.
Another and further object of the present invention is to provide an improved green, porcelain tooth, and method of manufacture, which can be moistened and/or have moist porcelain added thereto without altering its basic shape or size, as by warping, wholly or partially disintegrating, etc.
Another object of the present invention is to provide an improved green, porcelain tooth and method of manufacture wherein a water-resistant or water-insoluble agglutinant or binder is utilized.
Yet another object of the present invention is to provide an improved green, porcelain tooth and method of manufacture wherein a water-soluble agglutinant or binder is utilized and said water-soluble agglutinant or binder is rendered water-resistant, either prior to shaping or molding or after shaping and molding.
A further object of the present invention is to provide an improved green, porcelain tooth and method of manufacture wherein a water-soluble agglutinant or binder is utilized and said agglutinant is rendered water-resistant by treating said agglutinant with a chemical which renders the said agglutinant or binder water-resistant, as by chemical reaction therewith, physico-chemical reaction therewith, mild heating during drying, exposure to light, physical combination therewith, etc., either before shaping or molding, after shaping or molding or during the drying of the shaped or molded structure.
A still further object of the present invention is to provide an improved green, porcelain tooth and method of manufacture wherein an agglutinant or binder is utilized which leaves no residue and thus does not affect the structure thereof, as the color, etc., when subsequently baked to the concretion point or the vitrification point.
Another and further object of the present invention is to provide an improved green, porcelain tooth and method of manufacture wherein an agglutinant or binder is utilized which is not expelled or destroyed, as by volatilization, etc., during drying, but is expelled by volatilization during baking to the concretion point or the vitrification point.
These and other objects and advantages of the present invention, as well as others obvious to one skilled in the art, will be apparent from the following description.